NiO-BASED CONTACTS FOR BLUE EMITTING DIODES

Jozef Liday - Ivan Hotový - Helmut Sitter - Klaus Schmidegg - Peter Vogrinčič - Juraj Breza - Alberta Bonnani

   Auger electron spectroscopy (AES) depth profiling in combination with the circular transmission line method (CTLM) contact resistivity measurements of the Au/NiO_x/p-GaN contact scheme with various content of oxygen in the NiO_x layer were used to explain the reduction of the contact resistivity as a result of its annealing in oxygen ambient. Au/NiO_x layers with a small concentration of oxygen in NiO_x were deposited on p-GaN by reactive dc magnetron sputtering and annealed in a mixture of O₂ and N₂, and in N₂ ambient. It was found that the Au/NiO_x/p-GaN structure with a low concentration of oxygen in the NiO_x layer provides a low resistivity ohmic contact, no matter if it is subsequently annealed in N₂ or O₂+N₂ ambient at 500 °C for 2 minutes. Auger depth profiles reveal that while annealing in O₂+N₂ ambient results in reconstruction of the initially deposited Au/NiO_x/p-GaN contact structure into a NiO/Au/p-NiO/p-GaN structure, annealing in N₂ brings about reconstruction into Au+Ni/p-NiO/p-GaN.

Keywords: Auger electron spectroscopy, depth profiling, gallium nitride, nickel oxide

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